Depends how much tiling your going to do.

If it's just for a one off job or diy then theres not much point spending hundreds of pounds....and a cheapie will suffice

I personally use a cheapie.  Lasts a few jobs and then it gets binned.

The best advice i can give you is get the most powerful one you can afford and pay attention to the fence, this seems to be the weak point on the bargain basement jobbies

I've got the plasplugs cheapie and I've been using it for nearly two years doing about one tiling job a month on average. It must have gone through thousands of tiles (mostly cheap white wall tiles). I've changed the disc once but even then it wasn't that worn out. Keeping the water level high and not pushing hard helps. It's always had a slight angle to the disc, and I found the guide too much hassle because of the disc's angle. But cutting without the guide and following the grooves with my fingers as I feed in the tile is just as good. I've got an old fashioned tile cutter as well, but with all the awkward cuts it's just as easy to use the disc cutter than fiddle with both.